fuel pump

Check fuse #10 in the engine compartment. If okay then check fuel pump relay. You can do that by swapping out with another relay like headlights or horn as long as they are the same. If still no fuel pressure with a test lamp back probe the grey wire to fuel pump. If it lights up then the fuel pump is actually bad and you should be good on your repair. When you check it, have someone turn the key on. The light will just come on for a second then go out. While cranking the test light will come on again. If the test light does not light up then there is a problem in the circuit like a burnt terminal under the fuse box?

i just want to know how to test the new fuel pump before i replace it.

I just want to know how to bench test the new fuel pump before I replace it.

Apply battery voltage and ground

Added the diagram. The 2 pins you need to apply battery power and ground are the 2 middle pins on the fuel pump side. If you have a power probe it will be much easier. On the pump from left to right the 2nd pin is power and 3rd pin is ground. Hope that helps.

i replace the fuel pump and fuel filter on a 2004 GMC envoy SLT 4.2L the first time i check the fuel pressure after i replace the new fuel pump it show about 56psi what is the fuel pressure supose to be? the test port is connect to the fuel line at the fuel filter there is where i check the pressure is there another test port under the hood where i can test the pressure there? the engine will crank but want start when i turn the key to run the pump will run for about 2 second and sometime the pump keep on running want stop until i turn the key off what cause the pump to keep on running?

That is the only port available. Spec calls for 50-57 psi key on engine off.

Scan the vehicle for codes. If you have fuel pressure then check for spark and injector pulse also.

the battry cable been disconnect will that erase the codes? i will scan again, where are the injector located? i look for the injector couldn't find it can you send pictures? i did check for spark i did see a spark but the battry is low and the engine wasn't turning fast enough so the spark was a hit and miss.

If battery was disconnected then the codes will reset. The fuel injectors are under the intake manifold.